1. Field of the Invention
The present invention discloses a pressure differential operated or direct acting safety valve.
2. Description of Related Art
Gas storage wells are frequently located in depleted hydrocarbon reservoirs at a relatively shallow depth less than five thousand feet. Common characteristics of gas storage wells are relatively low flowing pressures, less than three thousand psi, a large unrestricted flow area and high flow rates with frequent variations in the flow. Examples of subsurface safety valves particularly adapted for use in gas storage wells are shown in U.S. Pat. Nos. 3,481,362; 3,459,260; and 3,491,831. Each of these patents was invented by William W. Dollison and assigned to Otis Engineering Corporation. U.S. Pat. Nos. 3,481,362; 3,459,260; and 3,491,831 are incorporated by reference for all purposes within this application.
Direct acting subsurface safety valves, which are closed by an increase in the fluid flow rate through the valve, are shown in U.S. Pat. No. 3,070,119 invented by George M. Raulins and U.S. Pat. No. 3,126,908 invented by George C. Dickens. Both of these patents disclose using a ball type detent mechanism to hold the respective valve closure means open until the flow rate through the respective valve exceeds a preselected value. U.S. Pat. Nos. 3,070,119 and 3,126,908 are incorporated by reference for all purposes within this application.
A direct acting subsurface safety valve, which is closed by a preselected rate of pressure differential change, is shown in U.S. Pat. No. 4,339,001 invented by James H. Paschal, Jr. This patent discloses a ball type detent mechanism to hold the valve open until the rate of change of fluid pressure within the valve exceeds the preselected value. U.S. Pat. No. 4,339,001 is incorporated by reference for all purposes within this application.
Various types of direct acting subsurface safety valves are commercially available under the trademark STORM CHOKE.RTM., registration number 695,910, assigned to Otis Engineering Corporation.